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2006 Streets, Gem Lake, Minnesota - Geotechnical Recommendations January 18, 2006 Page 2 Table 2. Soil Conditions Beneath Bituminous and/or Aggregate Base Street Soil Description 1 to 3 feet of fill consisting of silty sand, clayey sand, and lean clay Tessier Road underlain by alternating layers of silty sand, sand with silt, poorly graded sand, and claye sand Haven Lane 2 feet of silty sand and clayey sand fill underlain by 4.5 feet of clayey sand, underlain by 2.5 feet of silty sand with gravel, underlain by sand 2 feet of fill consisting of silty sand with gravel, underlain by 2 feet of Little Fox Lane clayey sand, underlain by 2.5 feet of silty sand, underlain by sand and sand with gravel 2.5 to 9 feet of fill consisting of lean clay with sand, lean clay, clayey Big Fox Road sand, silt, silty sand, and sandy lean clay. The underlying soils are mainly sand in the north part of the street, silty sand in the middle of the street, and sandy lean clay/clayey sand in the south part of the street. No ground water was encountered during drilling in any of these borings. Pavement Section The recommended pavement section for all streets is as follows: 1.5 inches LVWE35030C Bituminous Wear Course 2.0 inches LVWE35030C Bituminous Wear Course 6.0 inches Class 5 Aggregate Base Course The bituminous mixes all follow Mn/DOT Standard Specification 2360. The aggregate base course follows Mn/DOT Standard Specification 3138. This is based on an R-value of 20 for Tessier Road and an R-value of 10 for Haven Lane, Little Fox Lane, and Big Fox Road. The 20 year ESAL for each road is 20,000. However, at these low traffic volumes, the pavement section is governed by constructability instead of traffic. When taking into consideration the select granular borrow in the subgrade (discussed below), the G.E. of the pavement section is 19.8, which is adequate for a 20 year ESAL of 100,000. Pavement Subgrade Preparation Due to sandy lean clay and clayey sand subgrade in many locations on Haven Lane, Little Fox Lane, and Big Fox Road, as well as the silty sand at Tessier Drive, we recommend that a minimum of 1 foot of select granular borrow (Mn/DOT 3149.2) be placed beneath the aggregate base course on these streets. Prior to placing the select granular borrow, test roll the existing soils according to Mn/DOT 2111. Place perforated PE drain tile at the bottom of the select granular borrow, underneath the back of the curb or the edge of the pavement on each side of the street. The drain tile shall have a minimum diameter of 3 inches and be wrapped in a Type I geotextile sock (Mn/DOT 3733). Connect the drain tile to catch basin or manhole structures, or daylight it at a slope. If the drain tile is daylighted at a slope, connect the pipe to a headwall where it daylights. Mn/DOT Standard Plate 3131 C is a suitable headwall. The drain tile shall discharge to a structure or slope at intervals of not more than 400 feet.